Once again you need to remember the putting stroke is an arc, not a straight line. It is not a straight line because the ball is to the side of you. You want to get the putter shaft in line with your forearms. Getting them in line with your forearms will allow you to make that arcing motion. I have said many times that my philosophy is to allow you to do things in your golf game. I don't want you to make a lot happen. The reason is simple. You don't have time to make a lot happen. The more you allow it to happen the easier it is. A great way to work on this is again with a mirror. Lay your putter up against the mirror as it would be soled correctly at address. Take a piece of masking tape and place it on the mirror on the same angle as the shaft. Stand in front of the mirror and get the club in line with the tape then get your forearms in line with your club shaft. You will need to 'fidget' with it by either bending your elbow either more of less. Keep working on it until you find that angle and then keep it in your putting stroke.